The objective of this project is to develop biochemical methods for studies of action potential and receptor ionophores leading eventually to isolation of these macromolecules and characterization at both the molecular and cellular levels. Our current efforts are directed toward developing reagents, mainly neurotoxins, which act on the action potential Na ion ionophore, preparing radioactively labelled derivatives, and using these reagents to characterize the ionophore at the cellular level and to solubilize and eventually isolate it. The nicotinic acetylcholine receptor ionophore is also under study at the cellular level.